Grooved Lid for Packaging of Fresh Fruits, Vegetables and Flowers in Corresponding Modified Atmosphere Trays

ABSTRACT

This invention relates to novel designs of tray lids and tray bases for modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, this invention relates to novel designs of landscaped lids and corresponding tray bases which enable cooling air to be circulated in single or multiple directions through stacked lid and tray combinations that contain fresh fruits, vegetables and cut flowers in a modified atmosphere environment. The gas-permeable modified atmosphere package comprises a lid constructed of a polymer, the lid having on the top surface thereof at the mid-regions of each side a plurality of raised load supports and in between grooves; and a base with a hollow interior constructed of corrugated kraft paper polymer and having a configuration at the top edges which conforms with the interior profile of the lid; the grooves enabling air to be circulated over the lid when one package combination is stacked on another.

TECHNICAL FIELD

This invention relates to novel designs of tray lids and tray bases for modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, this invention relates to novel designs of landscaped lids and corresponding tray bases which enable cooling air to be circulated in single or multiple directions through stacked lid and tray combinations that contain fresh fruits, vegetables and cut flowers in a modified atmosphere environment.

BACKGROUND

The quality attributes of fresh fruits, vegetables and cut flowers should be maintained as much as possible for as long as possible to ensure consumer acceptability. Quality deterioration of horticultural produce such as fresh fruits, vegetables and flowers comes about through inherent plant tissue enzyme reactions including respiration, ripening and senescence. Deterioration also occurs through microbial growth and water loss from the tissue. A method of inhibiting the deteriorative enzyme reactions, and the growth of yeasts, molds and bacteria in fresh produce involves the reduction of the produce temperature to between 1° and 12° C., and the creation of low O₂/high CO₂ modified atmosphere (MA) around the produce. Another quality reducing factor is that water in fruits and vegetables can be lost readily under low relative humidity conditions thereby causing dehydration, skin wrinkling, wilting and reduction in crispness and firmness of the fruits, vegetables and flowers. The rate of water loss from such fresh produce can be restricted by storing the produce in closed package systems consisting of walls with low moisture permeability.

Corrugated paperboard boxes and cartons are used commercially for the storage and transport of fresh horticultural commodities. Advantages of corrugated paperboard boxes and cartons include relatively low cost per unit volume, low thermal energy conductivity, impact absorption which prevents bruising of commodities and ease of disposal at the receiving end of the shipping route. One type of globally used corrugated paperboard box is known as a Eurotray. It has a standard horizontal dimension of 40 cm width and 60 cm length which is compatible for storage in stacks on pallets in ISO conforming containers.

Conventional corrugated paperboard has a very high gas and moisture permeability and as such is unsuitable for modified atmosphere packaging of horticultural produce. The fresh produce industry incorporates the use of stackable corrugated fiberboard cartons or returnable plastic crates of various sizes and shapes to accommodate a wide array of fresh fruits and vegetables for transportation to market. In general, there are two broad categories of stackable fiberboard cartons used in the produce industry, namely open style cartons which incorporate apertures such as hand-holds and concavities for refrigerated air circulation and closed style cartons which do not include the apertures and concavities but incorporate selective gas permeable membranes to limit gas exchange between the interior headspace of the sealed cartons and ambient atmosphere.

Open style cartons are advantageous because they allow for direct field packing of the harvested produce in the cartons, followed by refrigeration and shipment to market. The simple packaging and cooling of the produce provides significant time, labor and cost savings. A main disadvantage of this type of packaging is that the free movement of oxygen around the harvested produce maintains produce respiration rates and thus reduces the amount of time the produce can be stored and/or transported without quality deterioration. To offset some of these deleterious effects, produce is conventionally harvested earlier in the growing season while the produce is still green. This is before optimal nutritional values and desirable tastes have developed in the produce, thus reducing the quality of the produce delivered to market. Another disadvantage of the open style packaging is the minimal protection afforded to ambient temperature fluctuations frequently encountered during transportation to market.

Closed style cartons, known also as modified atmosphere packaging (MAP), have an advantage because the produce can be harvested when ripe. Such packaging of fruits, vegetables and flowers involves:

-   1. Harvesting the produce at full ready-to-eat maturity; -   2. Pre-packaging treatment of the produce, including sanitizing,     grading and pre-cooling; -   3. Packing of the produce in a controlled gas-permeable package     system; -   4. Introduction of a predetermined CO₂ and O₂ containing gas mixture     into the headspace of the package system or the retention of     existing air in the head-space of the package system; -   5. Closure and sealing of the modified atmosphere (MA) package     system; and -   6. Re-cooling of the packaged produce to transport temperature.

During storage, the fruits, vegetables and flowers respire and convert O₂ from the headspace to CO₂ with the result that the O₂ content in the headspace decreases while the CO₂ content increases. The respiring fruits, vegetables or flowers generate heat which offsets refrigeration. An objective in the design of an effective package system for MAP of fresh produce is to regulate the influx of O₂ into the package and the efflux of CO₂ from the package headspace. In this way, it is possible to achieve and maintain a desirable low O₂, high CO₂ modified equilibrium atmosphere and controlled temperature in the headspace around the stored produce for optimum retention of the fresh quality attributes and for the reduction of microbial growth while the fruits, vegetables and flowers are being shipped from source to destination, and storage at the destination.

Low levels of O₂ and elevated levels of CO₂ in the headspace around a horticultural commodity reduce the respiration and ripening rates, and the growth of spoilage organisms (spoilogens) of the commodity. Unsuitable modified atmospheres around fresh produce in a package system can induce physiological damage, inhibit wound healing, enhance senescence and cause formation of off-flavor components in the produce. Oxygen levels of less than 1% vol. bring about anaerobic respiration and off-flavor development, whereas CO₂ levels of about 10% vol. or higher inhibit microbial growth. CO₂ levels greater than 20% vol. over an extended period may cause tissue damage to CO₂-sensitive fresh produce.

Package systems for MAP must be designed and constructed with specific packaging materials to meet the following requirements:

-   1. Maintain definitive beneficial equilibrium levels of CO₂ and O₂     in the headspace of the package system; -   2. Obviate gas pressure build-up within the package system; -   3. Minimize moisture loss from fresh produce contained in the MA     package; -   4. Prevent fresh produce crushing and bruising; -   5. Inhibit water migration from the package interior into the walls     of the package system to thereby retain structural strength of the     walls; and -   6. Transmit fresh product respiration heat away from the package     system.

The gas and moisture permeabilities of the package components of MA package systems are critical parameters. The technology of plastic polymeric films has advanced to such an extent that a specific gas permeability requirement can be met with a single plastic film or a multi-layer film combination, with or without vent pinholes.

In 1960, Eaves (J. Hort. Sci. 37:110, 1960) reported the effectiveness of gas-permeable, flexible polymeric barrier film as a package system for extending the life of fresh commodities. Tomkins (J. Appl. Bacteriol. 25:290, 1962) used polymeric film-covered trays as package systems to determine their effectiveness in establishing equilibrium MA around apples. Prior art on the use of bags made from polymeric plastic, gas permeable film such as polyethylene and polyvinylchloride, for prolonging of shelf-life of stored fruits and vegetables, is exemplified by U.S. Pat. No. 3,450,542, Badran, U.S. Pat. No. 3,450,544, Badran et al., and U.S. Pat. No. 3,798,333, Cummin. A more complex package system has been described by Rumberger (U.S. Pat. No. 3,630,759) in that an inner plastic pouch containing the produce is enveloped by an outer pouch containing an atmosphere of less than 15% O₂. Both pouches are to be constructed from gas-permeable films.

U.S. Pat. No. 5,575,418, issued 19 Nov. 1996, Wu et al., relates to novel package systems for refrigerated modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, the patent discloses the design, construction, closure, sealing and use of gas-permeable corrugated paperboard package systems for prolonging the storage life of fresh fruits, vegetables and cut flowers under modified atmosphere in the headspaces of the closed package system. The corrugated gas permeable paperboard comprises: (a) a first layer of kraft paper; (b) a layer of polymer having a gas permeability which permits gas to be transmitted through the polymeric film at prescribed levels; (c) a second layer of kraft paper, said first and second layers of kraft paper sandwiching the polymer between them; (d) a corrugated fluting; and (e) a third layer of kraft paper affixed to the corrugated fluting.

U.S. Pat. No. 5,609,293, issued 11 Mar. 1997, Wu et al., relates to the design, construction and use of lined or coated corrugated paperboard package systems (e.g. boxes, cartons) for prolonging the storage life of fresh fruits and vegetables under modified atmospheres (MA) in the headspaces of the closed package systems. The plastic-paperboard construction comprises a first layer of polymeric film, a second layer of kraft paper adjacent the first layer, a kraft paper corrugated flute adjacent the second layer and a fourth layer of kraft paper adjacent the flute.

U.S. Pat. No. 6,050,412, issued 18 Apr. 2000, Clough, et al., relates to a novel method and apparatus for packaging and shipping horticultural products including cut flowers. In particular, the patent discloses a novel method of and packaging for packaging cut flowers in a modified atmosphere package to prolong shelf life in shipping the packaged flowers to the destination, and then at the destination, opening the package and rehydrating the cut flowers in the package by saturating the stems of the flowers with water.

Patent Cooperation Treaty application Serial No. PCT/CA2006/001404, 25 Aug. 2006, discloses novel Eurotray compatible package systems for refrigerated modified atmosphere packaging of fresh fruit, vegetables and cut flowers. More particularly, the application relates to the design, construction, closure, sealing and use of gas-permeable paperboard package systems and shipping trays for prolonging the storage life of fresh fruits, vegetables and cut flowers under modified atmosphere in the headspaces of the closed package system. A gas permeable paperboard comprising: (a) a first layer of kraft paper; (b) a layer of polymer having a gas permeability which permits gas to be transmitted through the polymeric film at prescribed levels; (c) a second layer of kraft paper, said first and second layers of kraft paper sandwiching the polymer between them.

None of the foregoing cited references discloses a stackable lid and tray system which incorporates modified atmosphere technology, allows single or dual angular direction cooling and ventilation of stacked and/or palletized packages or facilitates visual inspection of the package contents without opening the sealed package.

There is a need for a closed stackable lid and tray package system which incorporates modified atmosphere technology, allows harvesting and packaging of produce in either the field or in a centralized facility, allows single or dual direction of cooling and ventilation of stacked and/or palletized packages to offset produce respiration, allows visual inspection of the packaged produce at any point following packaging and provides the ability to refrigerate the fresh produce during transit.

U.S. Pat. No. 6,880,748,B2, Machado, discloses a modified atmosphere packaging system and method which allows field and/or centralized facility packing of fresh produce and refrigerated air to circulate throughout a palletized stack of cartons. The packaging includes a transparent lid with raised stacking supports at the four corners. The lid is sealingly attached to a corrugated fiberboard carton with a gas permeable membrane. The transparent lid allows for inspection of perishable produce contained therein without breaching an established modified atmosphere. A problem with this system is that when the cartons are stacked on one another, unless care is taken to ensure that the upper carton is squarely mounted on the lower carton, the lower corners of the upper carton can miss the corner supports and drop into the grooves in the lid on the lower carton. Another shortcoming is that the total surface area of the raised supports at the four corners of the carton is not large and load bearing capability is minimized.

The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

SUMMARY OF THE INVENTION

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

The invention is directed to a gas-permeable modified atmosphere package combination comprising a lid constructed of a polymer, the lid in one embodiment having on the top surface thereof at the mid-regions of each side a plurality of raised load supports and in between grooves; and a base with a hollow interior constructed of corrugated kraft paper polymer and having a configuration at the top edges which conforms with the interior profile of the lid; the grooves enabling air to be circulated over the lid when one package combination is stacked on another.

The top surface of the lid can have around its periphery at least one raised load support in the mid-region of each end and at least one raised load support in the mid-region of each side, and a depressed area between the raised end and side load supports. The top surface of the lid can have around its periphery at least two raised load supports in the mid-region of each end and at least three raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports. The top surface of the lid can have around its periphery at least two raised load supports in the mid-region of each end and at least four raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports.

The corners of the top surface of the lid can have diagonal grooves therein. The grooves at the sides of the lid can be disposed laterally while the grooves at the ends of the lid can be disposed longitudinally. The grooves of the surface of the lid can have an “X” type pattern. The lid and the base can be 60 cm in length and 40 cm in width.

The base can comprise a first outer layer of kraft paper, a first intermediate layer of corrugated kraft paper, a second intermediate layer of polymer and a second outer layer of kraft paper. The polymer in the base can be selected from the group consisting of ethylene vinylacetate (EVA), ethylbutyl acetate (EBA), a crosslinked ionomer resin, cast polyester (PET), a polyamide and polycarbonate (PC). The polymer can be low density polyethylene or high density polyethylene, or a copolymer of low density polyethylene and ethylenebutylacetate.

The gas permeability of the polymer of the base can be between about 50 and 100,000 cc³/m² 24 hr. 1 atm.

The invention is also directed to a lid for a gas-permeable modified atmosphere package comprising a top surface which can be rectangular or square, said surface including a plurality of raised load supports and in between grooves arranged around its periphery, the grooves enabling air to be circulated over the lid when one package is stacked on another.

Each end of the lid can have in the mid-region thereof at least one raised load support and each side of the lid can have in the mid-region thereof at least one raised load support and a depressed area can exist between the raised end and side load supports. Each end of the lid can have in the mid-region thereof at least two raised load supports and each side of the lid can have in the mid-region thereof at least three raised side supports. Each end of the lid can have in the mid-region thereof at least three raised load supports and each side of the lid can have in the mid-region thereof at least four raised side supports.

The grooves at the sides of the lid can be disposed laterally while the grooves at the ends of the lid can be disposed longitudinally. The top surface of the lid can have diagonally disposed grooves at each of the four corners of the lid. The lid can be formed of transparent polymer.

The lid can have a planar top surface and can be formed of a transparent material. The top surface of the lid can be quadrilateral such as square or rectangular and the transparent material can be a transparent polymer. The lid can be deployed on a hollow base constructed of paperboard.

The lid can be formed of transparent polymer, can have a top surface with a square configuration and a plurality of raised load supports and in between grooves positioned around its periphery. The raised supports can be located at the mid-regions or the corners of the top sides of the lid.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

FIG. 1 illustrates an isometric view of a lid with a plurality of raised supports and in between grooves around the circumference of the lid for packaging fruit and vegetables, according to a first embodiment of the invention.

FIG. 2 illustrates an isometric view of a corresponding tray base for the lid illustrated in FIG. 1.

FIG. 3 illustrates an isometric view of a lid with a plurality of raised supports around the circumference for packaging cut flowers, according to a second embodiment of the invention.

FIG. 4 illustrates a corresponding tray base for the lid illustrated in FIG. 3.

FIG. 5 illustrates an isometric view of an “X”-grooved lid, according to a further embodiment of the invention.

FIG. 6 illustrates an isometric view of a tray base for the lid illustrated in FIG. 5.

FIG. 7 illustrates a plan view of the lid illustrated in FIG. 1.

FIG. 8 illustrates a side elevation view of the lid of FIG. 7.

FIG. 9 illustrates an end view of the lid of FIG. 7.

FIG. 10 illustrates a section view of taken along lines A-A of FIG. 7.

FIG. 11 illustrates a plan view of a blank for a tray base, as illustrated in FIG. 2.

FIG. 12 illustrates a plan view of a standard ISO container with a grouping of pallets loaded with stacked lid and tray base containers according to the embodiment illustrated in FIGS. 1, 2 and 7 to 11 of the invention.

FIG. 13 illustrates a plan view of the lid illustrated in FIG. 3.

FIG. 14 illustrates a side elevation view of the lid of FIG. 13.

FIG. 15 illustrates an end view of the lid of FIG. 13.

FIG. 16 illustrates a plan view of a blank for a tray base, as illustrated in FIG. 4.

FIG. 17 illustrates a plan view of a standard ISO container with a grouping of pallets loaded with stacked lid and tray base containers according to the embodiment illustrated in FIGS. 3, 4 and 13 to 16 of the invention.

FIG. 18 illustrates a plan view of an “X” grooved lid as illustrated in FIG. 5.

FIG. 19 illustrates a side elevation view of the lid illustrated in FIG. 18.

FIG. 20 illustrates an end view of the lid of FIG. 18.

FIG. 21 illustrates a section view of the lid taken along lines A-A of FIG. 18.

FIG. 22 illustrates a plan view of a blank for a tray base, as illustrated in FIG. 6.

FIG. 23 illustrates a plan view of a standard ISO container with a grouping of pallets loaded with stacked lid and tray base containers according to the embodiment illustrated in FIGS. 5, 6 and 18 to 22 of the invention.

FIG. 24 illustrates an isometric view of a modified Eurobox with recessed sides and ends.

FIG. 25 illustrates an isometric view of a MAP box with a transparent lid.

FIG. 26 illustrates an isometric view of a modified Eurobox holding a plurality of MAP packages with transparent lids.

FIG. 27 illustrates an isometric view of an alternative embodiment of a MAP box with a plurality of raised supports around the circumference of the lid.

FIG. 28 illustrates an isometric view of a further alternative embodiment of a MAP box with raised supports at the corners.

FIG. 29 illustrates an isometric view of a further alternative embodiment of a MAP box with raised supports at the corners mounted on a MAP box base.

DESCRIPTION

Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

To deal with the long distance and the time required for continental and overseas shipment of MAP preserved fruits, vegetables and flowers, we have invented a unique family of lids having an uneven top surface comprising a series of raised load bearing areas around the circumference of the lid and grooves between the raised areas and a central depressed area. In one aspect, the invention includes a family of corresponding congruent tray base designs. Together the lid and tray base can be used for the shipment of fresh fruit such as grapes, peaches, nectarines and the like, vegetables such as sweet peppers, spinach, lettuce, tomatoes and the like, and fresh flowers in a modified atmosphere environment.

In one preferred version of the lid and tray base, the lid and tray base can measure 60 cm by 40 cm to conform with Eurotray standards. The modified Eurotray, according to the invention, has a top lid surface incorporating a plurality of raised supports around the circumference and a plurality of in between grooves. The grooves enable cooling air to circulate between Eurotrays when such trays are stacked on a pallet and stored in a refrigerator or shipped in an ISO conforming container. The cool air circulated through the stacked Eurotrays helps to offset heat generated by the respiring vegetables, fruit or flowers packaged in the Eurotrays. The top surfaces of the raised areas can be roughened or have a friction creating pattern thereon to enhance grip between trays when stacked.

A common request from customers of packaged fruits, vegetables and flowers is a capability of viewing the packaged product without opening the package. The lid of the subject invention is preferably formed of a transparent polymer.

Since the packaged product is refrigerated and since moisture is present in the interior of the package from respiration of the packaged fruit, vegetables or flowers, the interior of the lid typically collects condensation. The raised supports and grooved lid can, if desired, be molded from a polymer which contains an anti-fog agent. Alternatively, a moisture resistant agent can be applied to the interior surface of the lid.

A common problem with conventional modified atmosphere packaged fruit, vegetables or flowers is that they are packaged in corrugated paperboard containers which inherently provide insulation, which retains heat. If the fruit or vegetable product in the package is warm, time is required to cool the packaged fruit, vegetables or cut flowers to acceptable modified atmosphere refrigeration levels. A transparent lid is useful because it is reasonably heat conductive and transmits respiration heat from the packaged produce to the atmosphere, whereas conventional corrugated linerboard packaging inhibits heat transmission. The grooved surface of the lid enables cooling air to be circulated through stacked trays and thereby cool the produce quickly to refrigeration temperatures, and subsequently to maintain the produce in a cool condition.

Specific embodiments of the invention will now be discussed in association with the drawings. FIG. 1 illustrates an isometric view of a lid with a plurality of raised supports and in between grooves around the circumference of the lid for packaging fruit and vegetables, according to the invention. As seen in FIG. 1, the lid 2 is constructed of molded polymer, preferably transparent, such as polyethylene or acrylic, and has two groups of two raised wedge-shaped end supports 4 at the ends and two groups of three raised side supports 6 at the sides. These raised supports 4 and 6 are distributed around the periphery of the lid 2 and define between them a plurality of in between grooves and a central valley or depression 8 on the top of the lid 2. The lid 2 also includes two downwardly extending end panels 10 and two downwardly extending side panels 12. These end and side panels 10 and 12 fit over the top exterior of the base 14, as seen in FIG. 2. The lid 2 can be performed by any number of conventional techniques but vacuum molding or drawing is particularly suitable. Normally, the lid 2 is constructed of a gas-impermeable transparent polymer but it can, if required, be constructed of a suitable gas permeable transparent or non-transparent polymer. In one version, the lid can be 40 cm in width and 60 cm in length to conform with Eurotray standards. The top surfaces of the end supports and side supports 4 and 6 can be roughened to enhance friction grip when trays are stacked one upon the other.

FIG. 2 illustrates an isometric view of a corresponding tray base for the lid illustrated in FIG. 1. In particular, FIG. 2 illustrates a tray base with uneven top edges on the two sidewalls and the two end walls to conform with the interior contours of the end and side supports of the lid as shown in FIG. 1. As seen in FIG. 2, the one piece tray base 14 is constructed with two end panels 16 with upper edges 22 and two side panels 18 with upper edges 24, which respectively conform with the configurations of the interior of the two end supports 4 and the two side supports 6 of the lid 2 as shown in FIG. 1. The tray base 14 may be formed of conventional multi-layer corrugated kraft paper or two or more layers of kraft paper, with gas permeable polymer film between, such as constructions of the type disclosed in U.S. Pat. Nos. 5,575,418, 5,609,293 and 6,050,412. The two end supports 16 and the two side supports 18 form between them a bottom panel 20. It is understood that the top edges of the tray base may be even in elevation. However, it is preferred that the top edges be uneven because this adds strength to the lid and tray base combination.

FIG. 3 illustrates an isometric view of a lid with a plurality of raised supports around the circumference for packaging cut flowers according to a second embodiment of the invention. As seen in FIG. 3, the lid 26 is constructed of molded polymer, preferably transparent, such as polyethylene or acrylic, and has a pair of wedge-shaped raised end supports 28 and two groups of four side supports 30 at each side. These end supports 28 and side supports 30 are raised and define between them a plurality of grooves and a central valley or depression 36 on the top of the lid 26. The lid 26 also includes two downwardly extending end panels 32 and two downwardly extending side panels 34. These end and side panels 32 and 34 fit over the exterior of the tray base 38 as seen in FIG. 4.

FIG. 4 illustrates a corresponding tray base for the lid illustrated in FIG. 3. In particular, FIG. 4 illustrates a tray base with uneven top edges on the two side walls and two end walls to conform with the interior contours of the lid as shown in FIG. 3. As seen in FIG. 4, the one piece base 38 is constructed with two end panels 40 with upper raised edges 46 and two side panels 42 with raised upper edges 48. The two end panels 40 and side panels 42 define between them a tray base 44. The elevations of the top edges of the two groups of end panels 46 and four groups of side edges 48 conform with the interior configurations of the end supports 28 and side supports 30 of the lid 26 as shown in FIG. 3.

FIG. 5 illustrates an isometric view of a transparent “X”-grooved lid, according to a further embodiment of the invention. As seen in FIG. 5, the lid 52 is constructed of molded polymer, preferably transparent, such as polyethylene or acrylic, and has two broad area triangular raised end supports 54 and two broad area triangular raised side supports 56. These supports 54 and 56 define between them an “X” shaped valley or depression 57 on the top surface of the lid 52. The lid 52 also includes two downwardly extending end panels 58 and two downwardly extending side panels 50. These end and side panels 58 and 50 fit over the tray base 62, as seen in FIG. 2. The lid 52 can be formed by any number of conventional techniques, but vacuum molding or drawing is particularly suitable. In one version, the lid 52 can be 40 cm in width and 60 cm in length to conform with Eurotray standards.

FIG. 6 illustrates an isometric view of a tray base with uneven top edges on the two side walls and two end walls to conform with the interior contours of the lid 52 as shown in FIG. 5. Specifically, as seen in FIG. 6, the one-piece tray base 62 is constructed with two end panels 63 with upper edges 64 of two elevations and two side panels 65 with upper edges 66 of two elevations which respectively conform with the interiors of the two end supports 54 and the two side supports 56 of the lid 52 as shown in FIG. 5. The base 62 may be formed of conventional multi-layer corrugated kraft paper or two or more layers of kraft paper with a gas permeable polymer film between, such as constructions of the type disclosed in U.S. Pat. Nos. 5,575,418; 5,609,293; and 6,050,412. It will be understood that while uneven top edges of the base are shown, the invention includes bases with straight upper edges. Uneven upper edges which conform with the profile of the lid are preferred because this provides greater strength to the lid and base combination for stacking purposes.

FIG. 7 illustrates a plan view of the lid illustrated in FIG. 1. As seen in FIG. 7, the lid 8 has a pair of end supports 4 at each end, and a trio of side supports 6 at each side. These raised supports have grooves between them to enable cooling air to be circulated over the lids. The top surfaces of the end and side supports 4 are roughened to enhance grippability and discourage shifting when the trays are stacked.

FIG. 8 illustrates a side elevation view of the lid of FIG. 7. FIG. 8 illustrates the raised end supports 4, raised side supports 6 and side panel 12.

FIG. 9 illustrates an end view of the lid of FIG. 7. FIG. 9 illustrates the end panel 10, raised end supports 4 and raised side supports 6.

FIG. 10 illustrates a section view taken along section A-A of FIG. 7 and in particular, illustrates the central depressed area 8 and the pair of raised side supports 6.

FIG. 11 illustrates a plan view of a blank for a tray base, as seen in FIG. 2. In particular, FIG. 11 illustrates a paperboard blank 20 with a pair of side panels 18 and a pair of end panels 22. When folded along the stippled lines, the erected paperboard blank forms a tray base 14 with base 20 as illustrated in FIG. 2. The blank 20 is typically formed of corrugated paperboard. The arrow shown in FIG. 11 indicates the direction of the corrugated flutes that are in the interior of the paperboard blank 20. The triangular arrow denotes that the direction of the corrugated flutes of the paperboard from which the tray is formed. The flutes extend laterally rather than longitudinally. This flute orientation provides strength to the base. If the flutes extend longitudinally, the base 62 is prone to bending in a longitudinal direction.

FIG. 12 illustrates a plan view of a standard ISO container with a grouping of pallets loaded with stacked lid and tray base containers according to the embodiment illustrated in FIGS. 1, 2 and 7 to 1 of the invention. The arrow denotes the typical direction of air flow in the container.

FIG. 13 illustrates a plan view of the lid illustrated in FIG. 3. Specifically, FIG. 13 illustrates a plan view of a lid 36 used for shipping cut flowers according to the invention. The lid, as seen in FIG. 13, has a pair of raised wedge-shaped end supports 28 at each end and two groups of four raised side supports 30 on each side of the lid 36. The top surfaces of the end supports 28 and side supports 30 are roughened to enhance grippability so that when trays with lids are stacked, shifting is discouraged.

FIG. 14 illustrates a side elevation view of the lid of FIG. 13, including side panel 34 and raised end supports 28 and raised side supports 30. The grooves between the supports 30 are clearly shown.

FIG. 15 illustrates an end view of the lid of FIG. 13, including raised end supports 28, raised side supports 30 and end panel 32.

FIG. 16 illustrates a plan view of a blank for a tray base, as illustrated in FIG. 4. Specifically, FIG. 16 illustrates a paperboard blank 44, suitable for packaging and shipping cut flowers, including tray bottom 44, a pair of end panels 40 and a pair of side panels 42. Raised end edges 46 and raised side edges 48 are also shown. The arrow indicates the direction of the corrugated flutes in the paperboard that is used to make the blank illustrated in FIG. 16. The stippled lines indicate crease lines and when the blank is folded along the crease lines, the erected blank forms a tray base as illustrated in FIG. 4. The triangular arrow denotes that the direction of the corrugated flutes of the paperboard from which the tray is formed. The flutes extend laterally rather than longitudinally. This flute orientation provides strength to the base. If the flutes extend longitudinally, the base 62 is prone to bending in a longitudinal direction.

FIG. 17 illustrates a plan view of a standard ISO container with a grouping of pallets loaded with stacked lid and tray base containers according to the embodiment illustrated in FIGS. 3, 4 and 13 to 16 of the invention. The arrow indicates the typical direction of air flow in the container in which the palettes of trays are stored.

FIG. 18 illustrates a plan view of an “X” diagonal-grooved lid 52 of FIG. 5 with two raised broad area triangular end supports 54 and two raised broad area triangular side supports 56, which together form an “X” shaped channel, valley or depression 57 in the top of the lid 52. The lid 52 can be fitted over the top of the modified base 62 of FIG. 6 to provide a strong modified atmosphere package for shipping and stacking of fresh fruits, vegetables and cut flowers. The shaped channel between the two end supports 54 and side supports 56 enables air to be circulated between stacked Eurotrays. The broad areas of the four triangular shaped supports 54 and 56 provide broad load bearing sites so a reasonable number of trays can be stacked upon one another without distorting or crushing the bottom tray in the stack. The broad areas of the supports 54 and 56 also provide tolerance so that trays will still support one another, even though they may not be stacked in close alignment. The top surfaces of the supports 54 and 56 can be roughened to enhance grippability. The top surfaces of the supports 54 and 56 can have grooves therein to enhance air circulation over the top of the lids.

FIG. 19 illustrates a side elevation view of the Eurotray lid 52, with raised side support 56 and raised end supports 54, and side 60.

FIG. 20 illustrates an end view of the lid 52 with raised end support 54, raised side supports 56, and end panel 58.

FIG. 21 illustrates a section view taken along lines A-A of FIG. 18, showing the two side supports 56 and the central groove 57.

FIG. 22 illustrates a plan view of a corrugated paperboard blank for forming the tray base 62 illustrated in FIG. 6. The blank can include an intermediate layer of gas permeable film (not visible). The blank can be folded and erected to form a base 62 as shown in FIG. 6. The upper edges of the end panels 64 and the side panels 66 are visible. The triangular arrow denotes that the direction of the corrugated flutes of the paperboard from which the tray is formed. The flutes extend laterally rather than longitudinally. This flute orientation provides strength to the base. If the flutes extend longitudinally, the base 62 is prone to bending in a longitudinal direction.

FIG. 23 illustrates a plan view of a standard ISO container with a close grouping of pallets loaded with stacked containers according to a further embodiment of the invention. As seen in FIG. 23, each pallet, as indicated by the bold lines, bears three “X” Eurotray packages arranged in side by side relation and two “X” Eurotray packages arranged in end to end relation. The “X” shaped channels or grooves in the tops of the lids enable cooling air to be circulated through the stacked lid and base packages. Also, the triangular shape of the two end and two side supports provide large load bearing areas for stacked trays and minimize crushing.

FIG. 24 illustrates an isometric view of a modified Eurobox with recessed sides and ends. As seen in FIG. 24, the modified Eurotray 50 is sized to standardized shipping container specifications, namely 40 cm×60 cm, and has downwardly recessed sides 54 and downwardly recessed ends 56. In the embodiment shown in FIG. 24, the tray 50 also has reinforced corners 58, which enable the trays to be stacked. The recessed sides 54 and ends 56 enable refrigerated air to be circulated through both the sides and ends of stacked Eurotrays 40. The depth of the tray 50 can be increased two or more times to enable multiple layers of the boxes to be packed. A tray as shown in FIG. 24 is disclosed in U.S. patent application Ser. No. 11/458,951, filed 20 Jul. 2006.

FIG. 25 illustrates an isometric view of a MAP box embodiment of the invention. The MAP box 60 has a corrugated paperboard base 62 and a transparent lid 64, with downwardly extending sides 66 which fit snugly over the top and partially down the sides of the base 62. The transparent lid 64 enables the contents of the MAP box 60 to be viewed without opening the box 60. The sides 66 can be taped to the base 62 to provide a seal for the MA environment inside the box 60.

FIG. 26 illustrates an isometric view of a modified Eurobox holding a plurality of MAP packages. As seen in FIG. 26, the modified Eurotray 50, with reinforced corners 58 and recessed sides 54 and ends 56, is filled with rows of MA boxes 60. The MA boxes 60 are loaded with fresh fruit, vegetables or flowers, as the case may be. It will be recognized that while three rows of four, totaling twelve MA containers 60, are shown in FIG. 26, the sizes of the containers can be varied so that larger MA containers can fill the modified Eurotray 50, such as six or eight MA packages to a Eurotray. Also, it will be understood that the depth of the trays 50 can be increased to hold two or more layers of boxes 60.

FIG. 27 illustrates an isometric view of an alternative embodiment of a MAP box with a plurality of raised supports around the circumference of the lid. As seen in FIG. 27, the MAP box lid 70 has a plurality of raised supports 72 around its periphery. These supports 72 allow the MAP boxes to be stacked and permit air to be circulated through the grooves between the lids.

FIG. 28 illustrates an isometric view of a further alternative embodiment of a MAP box with raised supports at the corners. As seen in FIG. 28, the alternative design of MAP lid 74 has raised supports 76 located at the four corners. These supports 76 allow the MAP boxes to be stacked and permit air to be circulated through the grooves between the lids.

FIG. 29 illustrates an isometric view of a further alternative embodiment of a MAP box with raised supports at the corners mounted on a MAP box base. As seen in FIG. 29, a MAP lid 70 as illustrated in FIG. 27 is mounted on a MAP box base 78. The raised supports 72 allow the MAP boxes to be stacked and permit air to be circulated through the grooves between the lids.

The modified lid and tray base are preferably sized to standardized shipping container specifications (ISO specifications), namely 40 cm width×60 cm length. The grooves in lid 2 of FIG. 1, lid 26 of FIG. 3, and the “X” configured diagonal-grooves in lid 52 of FIG. 5 enable refrigerated air to be circulated through both the sides and ends of the lid and base combinations when they are stacked, and maintain modified atmosphere packaged produce in optimum condition.

Storage life of fresh fruits and vegetables is dependent on storage temperature, gas composition around the produce and degree of physical abuse leading to bruises, abrasions and cuts. Storage and transportation of fruits and vegetables is facilitated by the packing of the produce in suitable package systems which provide features such as prolonging storage life, reducing physical abuse and lowering the rate of water loss of produce.

Corrugated paperboard boxes and cartons are used commercially for the storage and transportation of fresh fruits and vegetables for the following reasons:

-   1. Relatively low cost per unit volume; -   2. Low thermal conductivity; -   3. Impact absorbing ability to prevent produce bruising; -   4. Ease of disposal at the receiving end; and -   5. Moderate stacking strength.

Corrugated paperboard has very high O₂ and CO₂ permeabilities, so this material by itself is generally unsuitable for the construction of MA package systems. However, in the MAP lid and base package according to the invention, the base can be formed of a paperboard construction with an intermediate gas permeable film as disclosed in U.S. Pat. Nos. 5,574,418 and 5,609,293. By utilizing a gas-permeable polymer in the paperboard construction, the lid can be customized to provide a gas barrier or specific gas and moisture permeabilities.

In some cases, it may be advisable to have the lid formed of a gas permeable polymer. The gas permeable polymeric lid can be formed from homopolymers or copolymers produced as a monolayer or coextruded layers with specific formulation and caliper selected to produce the required oxygen (O₂) and carbon dioxide (CO₂) permeabilities. The polymers are usually selected from the polyolefin family, typically Low Density Polyethylene (LDPE), linear low density polyethylene (LLDPE), medium and high density polyethylene (MDPE and HDPE), polypropylene (PP). However, other polymers such as ethylenevinylacetate (EVA), ethyl butyl acetate (EBA), ionomer resins (cross-linked), cast polyester (PET), nylon (polyamide) and polycarbonate (PC) may also be considered.

A further unique embodiment of this invention is the ability of the base and lid to maintain internal equilibrium under varying gas compositions in the headspace. The gas permeability of the base and lid prevents a vacuum condition developing which can occur in conventional MAP systems if the packaged produce begins to absorb carbon dioxide. If such conditions were to develop in the permeable base and lid, the controlled influx of gases through the gas permeable polymer film in the base will not allow a deleterious vacuum to develop in the interior headspace of the lid and base.

For specific product applications, the rate of gas exchange within the base and lid combination may be achieved by controlled film porosity of the gas permeable intermediate polymer film layer. Porosity may also be achieved by piercing predetermined holes through the polymer containing inner liner either at the corrugating stage, die cutting operation, box forming stage, or in the completed box. Hole size, either single or multiple, may vary depending on the required gas exchange rate but typical hole diameters would be in the range of 0.25 to 2.00 mm. Hole positions on the base or lid will vary depending on the optimum location for each packaged product and the gas flow dynamics within the base and lid combination. Once the produce is packaged in the base and lid combination, the lid, if desired, can be sealed to the base by tape or some other sealing mechanism.

The oxygen (O₂) and carbon dioxide (CO₂) gas exchange rates through the lid and base of the invention should preferably be within the range 50-100,000 cc³/m² 24 hr. 1 atm.

It has also been found that the following additional factors must be critically controlled if consistent polymer characteristics are to be achieved:

-   Process conditions: Extrusion rate, melt temperature, melt pressure,     nip pressure, nip position, chill roll temperature, corrugating     process conditions, board die cutting conditions. -   Polymer characteristics: Melt flow index, additives (processing     aids). -   Paper characteristics: Fibre length, virgin or recycled pulp, smooth     or rough side, with or without calender process.

The base, preferably of Eurotray dimensions, may be constructed of multiple layers of kraft paper, or of a plastic film membrane sandwiched between two sheets of kraft paper to form a tri-layer complex. The film membrane may be a gas-permeable plastic film or a plastic coating applied to one of the sheets of kraft paper, and then sealed between the two adjoining sheets. The membrane can be bonded to both of the kraft paper sheets when the plastic is in semi-molten state and the two paper sheets are pressed together.

When 25 g/m² low density polyethylene was used, and extrusion laminated on 40 g/m² and 125 g/m² MG kraft, the O₂ and CO₂ permeabilities were 1300 and 2200 cc/m² 24 hr. 1 atm. respectively. When a 35 g/m² coating of 17% EBA and LDPE was extrusion laminated, the O₂ and CO₂ permeabilities were 2300 and 4700 cc/m² 24 hr. 1 atm. respectively.

Studies have been carried out on fruits and vegetables packaged in sealed polymeric, plastic film bags in a corrugated paperboard box (Prince, 1989). However, several disadvantages of using a bag-in-a box are evident:

-   1. Loss of headspace around produce with the shrinkage of the bag     under negative pressure created by respiratory CO₂ dissolution in     the produce tissue; -   2. Extra handling of two packages, namely, the bag and the box; -   3. The thickness of the bag film must be at least 6 mil to ensure     bag durability during the handling, and thus high package cost and     low gas permeability of the bag is unavoidable. -   4. Thin plastic film serves as a cold surface for condensation of     water emitted from the produce, and can result in weight loss of     produce.

A benefit of injecting gas into an hermetically sealed MA box is that it is possible to include a trace gas, typically helium or sulphur hexafluoride as a leak detection method. Provided the MA box is relying on gas permeability and not porosity, it is possible to sense gas escape through cracks, unwanted pinholes or faulty glue seals.

Upon the insertion of a gas nozzle into the inlet aperture and upon the flow of the pressurized gas mixture through the headspace of the package system, plugs with vent pinholes or styrofoam plugs can be used for produce with high respiration rates and gas-impermeable plastic plugs may be used for low respiration rate produce.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. 

1. A gas-permeable modified atmosphere package combination comprising: (a) a lid constructed of a polymer, the lid having on the top surface thereof at the mid-regions of each side a plurality of raised load supports and in between grooves; and (b) a base with a hollow interior constructed of corrugated kraft paper polymer and having a configuration at the top edges which conforms with the interior profile of the lid; the grooves enabling air to be circulated over the lid when one package combination is stacked on another
 2. A combination as claimed in claim 1 wherein the top surface of the lid has around its periphery at least one raised load support in the mid-region of each end and at least one raised load support in the mid-region of each side, and a depressed area between the raised end and side load supports.
 3. A combination as claimed in claim 1 wherein the top surface of the lid has around its periphery at least two raised load supports in the mid-region of each end and at least three raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports.
 4. A combination as claimed in claim 1 wherein the top surface of the lid has around its periphery at least two raised load supports in the mid-region of each end and at least four raised side supports in the mid-region of each of the two sides of the lid, and a depressed area between the raised end and side load supports.
 5. A combination as claimed in claim 1 wherein the corners of the top surface of the lid have diagonal grooves therein.
 6. A combination as claimed in claim 1 wherein the grooves at the sides of the lid are disposed laterally while the grooves at the ends of the lid are disposed longitudinally.
 7. A combination as claimed in claim 1 wherein the grooves of the surface of the lid have an “X” type pattern.
 8. A combination as claimed in claim 1 wherein the lid and the base are 60 cm in length and 40 cm in width.
 9. A combination as claimed in claim 1 wherein the base comprises a first outer layer of kraft paper, a first intermediate layer of corrugated kraft paper, a second intermediate layer of polymer and a second outer layer of kraft paper.
 10. A combination as claimed in claim 1 wherein the polymer in the base is selected from the group consisting of ethylene vinylacetate (EVA), ethylbutyl acetate (EBA), a crosslinked ionomer resin, cast polyester (PET), a polyamide and polycarbonate (PC).
 11. A combination as claimed in claim 1 wherein the polymer is low density polyethylene.
 12. A combination as claimed in claim 1 wherein the polymer is high density polyethylene.
 13. A combination as claimed in claim 1 wherein the polymer is a copolymer of low density polyethylene and ethylenebutylacetate.
 14. A combination as claimed in claim 1 wherein the gas permeability of the polymer of the base is between about 50 and 100,000 cc³/m² 24 hr. 1 atm.
 15. A lid for a gas-permeable modified atmosphere package comprising a top surface which includes a plurality of raised load supports and in between grooves arranged around its periphery, the grooves enabling air to be circulated over the lid when one package is stacked on another.
 16. A lid as claimed in claim 15 wherein each end of the lid has in the mid-region thereof at least one raised load support and each side of the lid has in the mid-region thereof at least one raised load support and a depressed area exists between the raised end and side load supports.
 17. A lid as claimed in claim 15 wherein each end of the lid has in the mid-region thereof at least two raised load supports and each side of the lid has in the mid-region thereof at least three raised side supports.
 18. A lid as claimed in claim 15 wherein each end of the lid has in the mid-region thereof at least three raised load supports and each side of the lid has in the mid-region thereof at least four raised side supports.
 19. A lid as claimed in claim 15 wherein the grooves at the sides of the lid are disposed laterally while the grooves at the ends of the lid are disposed longitudinally.
 20. A lid as claimed in claim 15 wherein the top surface of the lid has diagonally disposed grooves at each of the four corners of the lid.
 21. A combination as claimed in claim 15 wherein the grooves of the surface of the lid have an “X” type pattern.
 22. A lid as claimed in claim 15 wherein the lid is rectangular and 60 cm in length and 40 cm in width.
 23. A lid as claimed in claim 15 wherein the lid is formed of transparent polymer.
 24. A lid as claimed in claim 15 wherein the polymer is low density polyethylene.
 25. A lid as claimed in claim 15 wherein the polymer is high density polyethylene.
 26. A lid as claimed in claim 15 wherein the lid has a planar top surface and is formed of a transparent material.
 27. A lid as claimed in claim 26 wherein the top surface of the lid is square or rectangular and the transparent material is a transparent polymer.
 28. A lid as claimed in claim 26 wherein the lid is deployed on a hollow base constructed of paperboard.
 29. A lid for a modified atmosphere box base wherein the lid is formed of transparent polymer, has a top surface with a square configuration and a plurality of raised load supports and in between grooves positioned around its periphery.
 30. A lid as claimed in claim 29 wherein the raised supports are located at the mid-regions of the top sides of the lid.
 31. A lid as claimed in claim 29 wherein the raised supports are located at the corners of the top sides of the lid. 